Do I need to add anything before sending a message to my friend in Russia?

If it is Belarus, try adding 375 in front.

If it's Russia, try adding 7 in front.

Just try it. I guess so. These numbers come from country codes. For example, when we send short messages in China, we will find that there are 86 in front of the mobile phone number, and 86 is the international long-distance country code of China.

But mind you, sending text messages abroad should be expensive. You'd better ask the service provider what the tariff is.

I hope I can help you:)